|A listing of Willard Gibbs unpublished fragments, wherein he lists entropy as "mixed-up-ness" as a draft stage idea.|
In the 1920 A System of Physical Chemistry by William Lewis and James Rice, state that “the molecules of a gas are in a continuous disordered movement, a gas being in fact a molecular chaos”.  They refer to Gibbs' description of entropy as mixed-up-ness and state that “this definition of entropy will be understood to a certain extent if we think of a substance as a molecular chaos … owing to collisions between the molecules their motion tends to become more and more disordered until a final stage of disorder is reached.”
They incorrectly state that “Gibbs considered that the degree of the disorder was identical with entropy” and that “when the disorder or chaos is greatest the entropy of a substance is likewise a maximum”. Gibbs, however, never once used the words “disorder” or “chaos”. 
1. Lewis, William and Rice, James. (1920). A System of Physical Chemistry, (pg. 48). Longmans and Green.
2. Mixed-up-ness (in the collected Scientific Papers of J. Willard Gibbs (Longmans), the reader will find on page 418 of the first volume a number of unpublished fragments, one subject bearing the title: Entropy as mixed-up-ness, a planned, but never finished, chapter).
3. Google book search of The Collected Works (Thermodynamics) and Elementary Principles in Statistical Mechanics.